Numerous test devices have been developed for the analysis of body fluids in order to determine the concentration of specific analytes in test samples. These include devices for detecting, for example, glucose, cholesterol, proteins, ketones, uric acid, phenylalanine, or enzymes in either blood or urine. Often tests are used to diagnose or treat a particular disease, such as diabetes or high blood pressure.
Two general types of test strips are in common use. Older devices require the application of a drop of blood to the top surface of a reagent pad, allowing the drop to react for a timed interval, removing the drop by wiping or blotting, and then determining the analyte concentration either visually or through the use of a reflectance photometer. Newer devices simplify the procedure by allowing the user to apply a drop of blood to a test strip while it is inserted in a meter. Optical and electronic elements within the meter detect the presence of blood, automatically start a timing and measuring process, and complete the analysis without removal of blood from the strip.
While the commonly used test strips are widely acclaimed and entirely satisfactory for many applications, the user of such test strips must bring the finger from which the blood drop has been obtained to the meter, rather than simply bringing the strip to the finger. Also, the deep red coloration of blood in the strip can interfere with a visual confirmation of the amount of color formed. Visual confirmation is a desirable indication of proper operation of the meter which reinforces user confidence in the accuracy of the concentration measurement. These disadvantages can be especially troublesome when the user is a patient suffering from disabilities related to a disease, such as diabetes, who must determine his own analyte concentrations. Such patients may have difficulty performing mechanical procedures required to operate conventional reagent strips.
Accordingly, there exists a need for a reagent strip which provides a test that requires only a single step in which the user can apply an unmeasured sample of whole blood and determine the concentration level of an analyte in a whole blood sample, either visually or through electronic viewing means.